1. Field of the Invention
This invention relates to a solid state imaging device wherein the corners including the image area of an imaging chip are chamfered and an electronic endoscope provided with the above mentioned solid state imaging device.
2. Related Art And Prior Art Statement
The imaging chip of a conventional solid state imaging device, for example, in a CCD is generally formed as shown in FIG. 1. An imaging chip 31 comprises an image area 32 consisting of a photodiode and vertical transfer lines, a horizontal transfer line 33 receiving electric charges from the final steps of the above mentioned vertical transfer lines, an output step 34 receiving an electric charge from the final step of this horizontal transfer line 33 and outputting it and electrodes 35 for transmitting and receiving signals and power sources for these respective parts. The above mentioned image area 32 is formed to be like a rectangle corresponding to the aspect ratio of a television displayed picture.
The above mentioned imaging chip is composed of silicon and is therefore enclosed within a package to improve the durability to the humidity and external force. As an example of a solid state imaging device enclosing the above mentioned imaging chip, there is such solid state imaging device enclosing an imaging chip in a ceramic package as is disclosed in the publication of Japanese Utility Model Application Laid Open No. 94650/1987 and shown in FIGS. 2(A) and 2(B). This imaging chip 41 is housed in an imaging chip housing recess 14 on a ceramic substrate 12 and is air-tightly sealed with a sealing glass 13 through a resin 16. As an example of making the package small, there is such solid state imaging device resin-sealing an imaging chip 42 with a transparent resin as is disclosed in Japanese Patent Application Laid Open No. 16683/1987 and shown in FIG. 3 and this imaging chip 42 is fixed and arranged on the package 17 and is resin-sealed with a transparent resin.
Now, an electronic endoscope has the above mentioned solid state imaging device arranged within an insertable section tip shown in FIG. 5 to be inserted into a body cavity or the like for observation and required to be fine in the diameter. This electronic endoscope is provided at the insertable section tip with a light guide emitting window 6a, an air and water feeding nozzle 7, a forceps channel 8 and an objective lens 9 as shown, for example, in FIGS. 5 and 6. A solid state imaging device 11 shown by the two-point chain line in FIG. 6 is arranged on the inner side of this objective lens 9.
If the above mentioned respective components are arranged so that the outside diameter of the tip part of the above mentioned electronic endoscope may be as fine as possible, they will be as shown in FIG. 6. If the respective outside diameters of the above mentioned respective components are set so that, for example, the diameter of the light guide 6 may be about 2.8 Mm, the diameter of the air and water feeding nozzle 7 may be about 2 mm, the diameter of the forceps channel 8 may be about 4 mm and further the image area 32 of the solid state imaging device 30 is set to be, for example, 3.times.3 Mm, the outside diameter of the above mentioned endoscope tip part will be about 9.1 Mm at the minimum.
On the other hand, as the image area 2 corresponding to the peripheral part of the above mentioned objective lens 9 lacks the incident light amount, the displayed picture of the above mentioned endoscope will become dark in the four corners. Also, by the characteristics of the lens, the resolution will reduce. In order to cope with this fact, as shown in FIG. 4, on the picture 22 of the endoscope image displaying monitor 21, the endoscope image displaying area 23 is chamfered in the four corners so as to be octagonal. This shows that, in the conventional purely optical medical endoscope, as the observing area shape is circular, even in the electronic endoscope, the shape of the displayed picture need not always be square and is well usable.
In case the area of the imaging surf ace of the above mentioned solid state imaging device is to be made as small as possible, it will be restricted by the contour dimension of the imaging chip. Also, the shape of the above mentioned imaging surface will be restricted by the shape of the above mentioned imaging chip and will therefore become rectangular. Further, in the case of the above mentioned electronic endoscope as an example of an instrument having a solid state imaging device built-in, in order to reduce the pain of the patient when the endoscope is inserted into the body cavity, it is preferable that the outside diameter of the tip part is as fine as possible but, if the outside diameter of the light guide is made fine, the illuminating light amount will decrease and the uniformly illuminatable illumination range will become narrow. In order that many kinds of forceps may be inserted in response to various medical treatments, it is preferable that the outside diameter of the channel is large. Therefore, in order that an instrument in which a solid state imaging device is arranged may be made small to the extremity, the above mentioned solid state imaging device must be able to be arranged within an area as small as possible.
As described above, in order that the imaging chip may be made small by the requirement of making small the instrument mounted with the above mentioned solid state imaging device, the area of the above mentioned imaging surface must be made small. However, there is a defect that, if the dimension of the above mentioned imaging chip is made small, the resolution and sensitivity will reduce.